The present invention related to the field of implantable hearing aid devices, and in particular, to implantable hearing aid microphones employable in fully- and semi-implantable hearing aid systems.
Traditional hearing aids are placed in a user""s ear canal. The devices function to receive and amplify acoustic signals within the ear canal to yield enhanced hearing. In some devices, xe2x80x9cbehind-the-earxe2x80x9d units have been utilized which comprise a microphone to transduce the acoustic input into an electrical signal, some type of signal processing circuitry to modify the signal appropriate to the individual hearing loss, an output transducer (commonly referred to in the field as a xe2x80x9creceiverxe2x80x9d) to transduce the processed electrical signal back into acoustic energy, and a battery to supply power to the electrical components.
More recently, a number of different types of fully- or semi-implantable hearing aid devices have been proposed. By way of primary example, implantable devices include those which employ implanted electromechanical transducers for stimulation of the ossicular chain and/or oval window (see e.g., U.S. Pat. No. 5,702,342), and those which utilize implanted exciter coils to electromagnetically stimulate magnets fixed within the middle ear (see e.g., U.S. Pat. No. 5,897,486). In these as well as other implanted devices, acoustic signals are received by an implantable microphone, wherein the acoustic signal is converted to an electrical signal that is employed to drive an actuator that stimulates the ossicular chain and/or oval window.
As may be appreciated, such implantable hearing aid microphones must necessarily be positioned at a location that facilitates the receipt of acoustic signals and effective signal conversion/transmission to an implanted actuator. For such purposes, implantable hearing aid microphones are most typically positioned in a surgical procedure between a patient""s skull and skin, at a location rearward and upward of a patient""s ear (e.g., in the mastoid region).
Given such positioning, the size and ease of installation of implantable hearing aid microphones are primary considerations in the further development and acceptance of implantable hearing aid systems. Further, due to the subcutaneous location of implantable hearing aid microphones, it is important that effective and efficient amplification be provided to yield a high fidelity signal. Relatedly, the componentry cost of providing such amplification is of importance to achieving widespread use of implantable system. Finally, it is important that the overall design of implantable microphones mitigate servicing/replacement needs.
In view of the foregoing, a primary objective of the present invention is to provide an implantable hearing aid microphone having a relatively small profile, particularly in the lateral extent.
Another objective of the present invention is to provide an implantable hearing aid microphone that reduces the extent of exposed surfaces for tissue attachment/infiltration, thereby reducing the potential need/periodicity of microphone servicing/replacement.
An additional objective of the present invention is to provide an implantable hearing aid microphone that is reliable and cost effective.
Yet further objectives of the present invention are to provide an implantable hearing aid microphone that is relatively robust and that provides for effective and efficient acoustic signal conversion to yield a high fidelity signal for middle ear stimulation.
One or more of the above objectives and additional advantages are realized in the implantable hearing aid microphone apparatus comprising the present invention. Such apparatus includes a housing having an internal chamber with an aperture thereto defined by a peripheral rim surrounding the aperture. A first diaphragm is sealably positioned across the aperture. Additionally, a microphone having a second diaphragm is disposed within the internal chamber to define an enclosed volume between the first and second diaphragms for mechanically amplifying acoustic signals received by the first diaphragm.
In one aspect of the present invention, the first diaphragm is recessed relative to the peripheral rim surrounding the aperture. More particularly, the first diaphragm may be preferably recessed between about 0.5 mm and 1.0 mm relative to the peripheral rim of the housing and across the lateral extent of the first diaphragm. Further, the outer edge of the peripheral rim may be disposed in a first plane and at least an outer face of the first diaphragm may be flat and disposed in parallel relation to the first plane.
In another aspect of the present invention, the internal chamber may be defined to comprise at least a first portion having a first cross-sectional area adjacent to the first diaphragm, and a second portion extending away from the first portion about an axis transfer to the aperture and/or first diaphragm and having a second cross-sectional area adjacent to the second diaphragm. Preferably, the first cross-sectional area is greater than the second-sectional area. Relatedly, it is preferable that the first diaphragm having an effective cross-sectional area (i.e., the area exposed for receipt of acoustic signals) that is at least about 100 times greater than the effective cross-sectional area of the second diaphragm.
The second portion of the internal chamber may adjoin the first portion internal chamber at a reduced opening therebetween, wherein the opening is smaller than and is positioned in opposing relation to the aperture. Further, the aperture and the opening may be coaxially aligned and may each be of circular configuration.
In one arrangement, the second portion of the internal chamber may be of an L-shaped configuration, wherein an opening between the first and second portions of the internal chamber is located at an end of a first leg of the second portion. In turn, the second diaphragm is positioned in a second leg of the second portion. Preferably, both the first and second legs of the second internal chamber portion, as well as the first internal chamber portion may, each be of a cylindrical configuration. Further, the first and second legs of the L-shaped second internal chamber portion may adjoin an internally rounded elbow.
In yet another aspect of the present invention, the first diaphragm may comprise a biocompatible material. By way of primary example, the first diaphragm may comprise a material selected from a group consisting of titanium and titanium-alloys. Further, it is preferable that the maximum cross-width of the first diaphragm (i.e., as measured across the area exposed for receipt of acoustic signals) established between about 8 and 15 millimeters, and most preferably between about 10-12 millimeters. Further, it is preferable that the first diaphragm thickness be established at between about 10 and 20 microns across the lateral extent thereof, and most preferably between about 12 and 15 microns.
By virtue of the above-noted features, an implantable microphone may be provided to reduce exposed surfaces for tissue infiltration. Further, a microphone may be constructed to reduce lateral space requirements upon surgical installation. Additionally, a microphone may be readily fabricated and assembled in a cost effective manner, while also yielding effective, high-quality signal amplification capabilities.
Additional aspects and advantages of the present invention will be apparent to those skilled in the art upon review of the further description that follows.